Polycarbonate resins are polymers in which aromatic or aliphatic dioxy compounds are connected to each other by a carbonate ester. Inter alia, a polycarbonate resin (hereinafter may be referred to as “PC-A”) obtained from 2,2-bis(4-hydroxyphenyl) propane (commonly known as “bisphenol A”) is excellent in not only transparency and heat resistance but also mechanical properties such as impact resistance and is therefore used in various fields.
The polycarbonate resins are generally produced by use of raw materials obtained from oil resources. However, since depletion of the oil resources has been concerned, production of polycarbonate resins using raw materials obtained from biogenic matters such as plants has been demanded. For example, an ether diol represented by the following formula (a):
is easily produced from sugar and starch, and three stereoisomers thereof are known. Specific examples thereof include 1,4:3,6-dianhydro-D-sorbitol (hereinafter referred to as “isosorbide”) represented by the following formula (b):
1,4:3,6-dianhydro-D-mannitol (hereinafter referred to as “isomannide”) represented by the following formula (c):
and 1,4:3,6-dianhydro-L-iditol (hereinafter referred to as “isoidide”) represented by the following formula (d).

The isosorbide, isomannide and isoidide are obtained from D-glucose, D-mannose and L-idose, respectively. For example, in the case of the isosorbide, it can be obtained by hydrogenating D-glucose and then dehydrating it by use of an acid catalyst.
Of the above ether diols, incorporation of the isosorbide in particular as a monomer into a polycarbonate has heretofore been studied.
For example, Patent Literature 1 proposes a homopolycarbonate resin having a melting point of 203° C. and produced by use of a melt transesterification method. Non-patent Literature 1 proposes a homopolycarbonate resin produced by a melt transesterification method using zinc acetate as a catalyst and having a glass transition temperature of 166° C. and a thermal decomposition temperature (5% weight reduction temperature) of about 283° C. Non-patent Literature 2 proposes a homopolycarbonate resin produced by interfacial polymerization using bischloroformate of isosorbide and having a glass transition temperature of about 144° C. Patent Literature 2 proposes a polycarbonate resin produced by use of a tin catalyst and having a glass transition temperature of at least 170° C. Patent Literature 3 proposes a copolymerized polycarbonate resin from isosorbide and a straight-chain aliphatic diol.
When application of these polycarbonate resins comprising isosorbide to industrial applications such as components for electric/electronic devices, components for OA equipment and automobile parts is considered, flame retardancy thereof must be studied. For example, the flame retardancy level according to UL-94 standard of a molded article having a thickness of 1.6 mm and made of a homopolycarbonate resin comprising isosorbide is not-V, and it needs an improvement in flame retardancy.
The polycarbonate resin comprising isosorbide has a different structure from that of a known bisphenol-A-type aromatic polycarbonate resin. Therefore, it is considered that its combustion mechanism is also different from a combustion mechanism proposed for the bisphenol-A-type aromatic polycarbonate resin, i.e. one in which a carbonized film is formed through intramolecular rearrangement and isomerization. Further, the polycarbonate resin comprising isosorbide also differs from the known bisphenol-A-type polycarbonate resin in compatibility with a flame retardant.
Accordingly, not all flame retardants used in the aromatic polycarbonate resin can be directly used in the polycarbonate resin comprising isosorbide, and alternative flame retardants must be studied.    (Patent Literature 1) Specification of UK Patent Application Laid-Open No. 1,079,686    (Patent Literature 2) Pamphlet of International Publication No. 2007/013463    (Patent Literature 3) Pamphlet of International Publication No. 2004/111106    (Non-patent Literature 1) “Journal of Applied Polymer Science”, 2002, Vol. 86, pp. 872 to 880    (Non-patent Literature 2) “Macromolecules”, 1996, Vol. 29, pp. 8,077 to 8,082